It's been a while since I've played Fallout 3, and I realised I've never played a sniper build, maybe because I didn't come across sniper rifles or sniper rifle ammo very easily. Anyway, I figured I'd give it a go now.

Any tips? How to get sniper rifle ammo and stuff? What should my SPECIAL start off as?

.308 rounds are always a pain to find, rivet city sells them, about 20 rounds each restock, if you have 6 luck and take scrounger, you can find more ammo for them easy. if youre a sniper, you should take along a backup pistol, maybe a silenced 10mm. as for a rifle, you can find one in the hollowed out rock, or make for the minefield right out of the vault and get one. if you have the pitt add on, you can use the ammo press for all the ammo you'll ever need. also if you have operation anchorage, you can cheat and get a near unbreakable sniper rifle and unlimited ammo. i guess snipers would have low strength, high perception, and maybe a companion so you can have a spotter.

You can get a sniper rifle right out of the Vault if you go behind Megaton and fight some mole rats. There is a stash under a rock surrounded by three small dead trees. I usually have Moira repair it as it's heavily degraded. Then you can head to Minefield and take out Arkansas and steal his rifle and loot his ammo. That's a good start for a sniper. As far as SPECIAL goes, I would think that Perception would be key, obviously, but beyond that it seems that it would be more a matter of your own personal preference.

oh yeah, if you take a left from the vault, you find a overpass with raiders, one at the end with a sniper.